Rules are typically used in business applications to guide or influence the business behavior in real-time. A majority of these applications need event-centric rules to monitor the creation of new business objects or some state changes in the business processes. An example of an event-centric rule, in the context of the travel business, is as follows: if a party reserves an airline ticket to Orlando and reserves a luxury car, offer a promotional discount to a particular Orlando hotel. Hence, upon the occurrence of the two events, the application would automatically offer the promotion to the party.
In the context of rules engines, rules are broadly divided into two classes: (1) deductive or inference rules; and (2) reactive or Event-Condition-Action (ECA) rules. The deductive rules use forward and backward reasoning to infer or deduce facts from existing knowledge bases. The ECA rules are well suited for event-centric problems, which deal with a state change and how to manage it.
Existing commercial rules engines act as repositories for business rules and facilitate the separation of the business logic from the application logic. Rules engines define some rule languages to allow declarative specification of rules and some interfaces to allow applications to interact with the rules engine. These rules engines are not suitable for multi-process event centric rule-based applications as there is no sharing between multiple rule engines running in individual application processes. The limited form of incremental rule evaluation in these engines is within the application process and this cannot be reused at a large scale.
In the publication entitled “Rule Activation Techniques in Active Database Systems” by Arie Segev, et al., only a small subset of the rule applications are considered, and a solution is proposed that uses relational tables to capture the results from incremental evaluation of rules. However this model uses one such table for each rule instead of grouping the rules in an application. Also, the types of rules supported by the approach described in the publication are limited to those testing for existence of conjunctive composite event types.
Based on the foregoing, there is room for improvement in the area of incremental evaluation of ECA rules in a database system.
The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.